Fix typing

src/fastmcp/client/client.py

@@ -18,7 +18,7 @@ from fastmcp.client.logging import (
     create_log_callback,
     default_log_handler,
 )
-from fastmcp.client.messages import MessageHandler, MessageHandlerFnT
+from fastmcp.client.messages import MessageHandler, MessageHandlerT
 from fastmcp.client.progress import ProgressHandler, default_progress_handler
 from fastmcp.client.roots import (
     RootsHandler,
@@ -143,7 +143,7 @@ class Client(Generic[ClientTransportT]):
         roots: RootsList | RootsHandler | None = None,
         sampling_handler: SamplingHandler | None = None,
         log_handler: LogHandler | None = None,
-        message_handler: MessageHandlerFnT | MessageHandler | None = None,
+        message_handler: MessageHandlerT | MessageHandler | None = None,
         progress_handler: ProgressHandler | None = None,
         timeout: datetime.timedelta | float | int | None = None,
         init_timeout: datetime.timedelta | float | int | None = None,

src/fastmcp/client/messages.py

@@ -1,5 +1,4 @@
-from collections.abc import Awaitable, Coroutine
-from typing import Any, TypeAlias, Union
+from typing import TypeAlias
 
 import mcp.types
 from mcp.client.session import MessageHandlerFnT
@@ -11,7 +10,7 @@ Message: TypeAlias = (
     | Exception
 )
 
-MessageHandlerFn: TypeAlias = MessageHandlerFnT
+MessageHandlerT: TypeAlias = MessageHandlerFnT
 
 
 class MessageHandler:
@@ -20,8 +19,13 @@ class MessageHandler:
     requests, notifications, and exceptions. Users can override any of the hooks
     """
 
-    def __call__(self, message: Message) -> Coroutine[Any, Any, None]:
-        return self.dispatch(message)
+    async def __call__(
+        self,
+        message: RequestResponder[mcp.types.ServerRequest, mcp.types.ClientResult]
+        | mcp.types.ServerNotification
+        | Exception,
+    ) -> None:
+        return await self.dispatch(message)
 
     async def dispatch(self, message: Message) -> None:
         # handle all messages

src/fastmcp/client/transports.py

@@ -24,7 +24,6 @@ from typing_extensions import Unpack
 import fastmcp
 from fastmcp.client.auth.bearer import BearerAuth
 from fastmcp.client.auth.oauth import OAuth
-from fastmcp.client.messages import MessageHandler
 from fastmcp.server.dependencies import get_http_headers
 from fastmcp.server.server import FastMCP
 from fastmcp.utilities.logging import get_logger
@@ -57,7 +56,7 @@ class SessionKwargs(TypedDict, total=False):
     sampling_callback: SamplingFnT | None
     list_roots_callback: ListRootsFnT | None
     logging_callback: LoggingFnT | None
-    message_handler: MessageHandlerFnT | MessageHandler | None
+    message_handler: MessageHandlerFnT | None
     client_info: mcp.types.Implementation | None